Psychophysical models for manual lifting tasks

This paper provides two models for males and females to assess the psychophysical maximum acceptable weight of lift. The weight guidelines generated by the models are a function of lifting frequency, height of lift, sagittal or asymmetrical lifting, task duration, container size in the sagittal plane, presence or absence of container couplings, and percentage of the working population. The developed models were generated from a knowledge base available in the published literature. A computer program was written in BASIC to assist the user in determining the safe load that could be handled by a specified working population. Model validation showed that the models developed predict the maximum acceptable weight of lift with a reasonable degree of accuracy. A comparison between the National Institute for Occupational Safety and Health recommendations and those made on the basis of the models developed in this paper is also presented.     

Subjective estimates of one-handed carrying tasks

In this study, ten male and five female subjects, ranging between 21 and 23 years in age and in excellent physical health, voluntarily participated. Four different shapes of containers, 8·5 and 12·3 litres in capacity, were used to carry loads for distances of 100, 200, and 300 ft (30·48, 60·96, and 91·44 m, respectively). Individuals first subjectively estimated how much weight they could carry in a given type of container for the required distance and then verified it by actual carrying. The preferred (stronger) hand was used to hold the containers. In addition to the weight acceptable for comfortable carrying, pulse rate and ratings of perceived exertion (RPE) of the arm and whole body were also used as response measures. Results indicated that subjects could quite accurately estimate the amount of weight they could carry comfortably in one hand. RPE for one-handed carrying tasks was not one-tenth of the pulse rate as is the case for whole body tasks. The average pulse rate was 100 beats/min for the weights selected. Shape of the containers significantly influenced the amount of weight subjects were willing to carry in one hand. The acceptable amount of weight decreased with distance, but was found to increase with volume.     

Polynomial-based optical true-time delay devices with microelectromechanical mirror arrays

We previously reported optical true-time delay devices, based on the White cell, to support phased-array radars. In particular, we demonstrated a quadratic device, in which the number of delays obtainable was proportional to the square of the number of times the light beam bounced in the cell. Here we consider the possibilities when a microelectromechanical (MEM) tip/tilt mirror array with multiple stable states is used. We present and compare designs for quadratic, quartic, and octic cells using MEM mirror arrays with two, three, and five micro-mirror tilt angles. An octic cell with a three-state MEM can produce 6,339 different delays in just 17 bounces.     

On the solution of hydrodynamical equations via Lie groups

Lie groups of homothetic transformations in the Euclidean space R₂ have been employed to determine and investigate certain classes of solutions of hydrodynamical equations of a perfect fluid. In particular, the conditions for a solution to be regular with respect to the one-parameter group of transformations have been determined. Furthermore, it has been shown that if the regularity conditions mentioned above are satisfied then the problem of obtaining regular solutions reduces to that of solving a system of equations not involving λ in the canonical coordinates (λ, μ) of the subgroup. Some special classes of flows have also been investigated.     

Effects on load handling of restricted and unrestricted shelf opening clearances

Changes in psychophysical lifting capacity with reductions in shelf opening clearances were experimentally determined. Three levels of shelf opening clearances were studied: unrestricted shelf opening clearance, loose shelf opening clearance (a clearance of 15 mm between the box width and the shelf opening), and tight shelf opening clearance (a clearance of 3 mm between the box width and the shelf opening). Two levels of lifting frequency (1 and 4 lifts/min.) and two lifting heights (floor to 0.81 m and 0.81 m to 1.52 m) were included. The metabolic energy expenditure rates and heart rates of the subjects (8 males and 8 females) at psychophysically acceptable weights of lift were also recorded to assess the physiological burden. The results indicated a decline in the psychophysical lifting capacity of the subjects as the shelf opening clearance became narrower. The decline in psychophysical capacity, compared to unrestricted shelf opening clearance for males was 9% when the shelf opening clearance was 15 mm. A further decline of almost 4% was recorded when the shelf opening clearance narrowed down to 3 mm. For females, the corresponding declines were approximately 10% and 4%. The effects of lifting frequency and height of lift were found to be consistent with previous findings.     

Antioxidative and antibacterial effects of seeds and fruit rind of nutraceutical plants belonging to the Fabaceae family

In the present study, the seeds and fruit rind of six plants of the Fabaceae family were selected to evaluate their potential as antioxidant and antibacterial agents. The dried powders were individually extracted with various organic solvents by the cold percolation method, were evaluated for antibacterial activity and methanol extracts used for antioxidant activities. Total phenol, protein and sugar contents were also measured. Antioxidant activities were measured by DPPH free radical scavenging activity, superoxide anion radical scavenging activity and reducing capacity assessment. Antibacterial activity was measured by the agar well diffusion method against four Gram positive and four Gram negative bacteria. The methanol extract of the fruit rind of C. indica showed the maximum DPPH free radical scavenging activity, superoxide anion radical scavenging activity, a high reducing capacity assessment and also had the highest total phenol content. There was a direct correlation between the phenol content and the antioxidant activity. The antibacterial activity of all the extracts was more pronounced on Gram positive bacteria than on Gram negative bacteria. Thus, the fruit rind of C. indica showed the best antioxidant and antibacterial activities.     

Optimization of Conditions for the Extraction of Antioxidants from Leaves of <Emphasis Type="Italic">Syzygium cumini</Emphasis> L. Using Different Solvents

The aim of the present study was to find out the best method for extracting antioxidants from Syzygium cumini L. leaves. The extraction was done by three different methods: sequential cold percolation extraction method, decoction extraction method, and maceration extraction method. Antioxidant activity, total phenol, and flavonoid content were determined in all different extracts of various extraction methods of S. cumini L. leaves. Antioxidant activity was tested by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical, superoxide anion radical and hydroxyl radical scavenging activities, and reducing capacity assessment. Sequential cold percolation extraction method proved to be the best extraction method. The acetone extract had maximum phenol and flavonoid content and showed best DPPH free radical scavenging activity and reducing capacity assessment. Ethyl acetate extract showed best superoxide radical scavenging activity, while aqueous extract showed best hydroxyl radical scavenging activity. It can be concluded that sequential cold percolation extraction method is the best method of extracting leaf antioxidants for this plant at least.